Secrecy communication system



June 1946- c. s. SZEGHO SECRECY COMMUNICATION SYSTEM Filed Nov. 13, 1943 1 i m m m M .0 W n M MW 6 tern is available which the letters 2.401.985 sponsor COCATION s s'ram Constantin The poration oil-Illinois S. Szegho, Chicago, 111., assignmto d Corporation, Chicago, Ill., a cor- Application November 13, 1943, Serial No. 510.129

9 Claims. (Cl. 178-22) This invention relates to new and useful im-- provements in secret communication systems and particularly in such systems which employ cathode ray tubes.

According to the present invention, a cathode ray tube is used, in a intelligence merely to indicate an ordinate sequence of light spots on a pattern. If a given patonly at the transmitting and the receiving ends, assured, since to all others the signals would represent only a meaningless sequence of spots. The letters of the pattern avoiding thus the coding and decoding of messages. I

In the drawing:

the secrecy of the transmission is.

the alphabet can be impressed on system of communicating As above stated, the same pattern is used at the transmitting as at the receiving end, and

the patterns used may be changed in any suitable prearranged member; At the receiver, the travel of the spot over the screen of the cathode ray tube can be controlled inaccordance with any, suitable scanning procedure. Since the definition of this kind of intelligence need not be high, if the object'be scanned with the employ- Fig. 1 diagrammatically represents one embodiment of this invention as applied to a receiver;

Fig. 2 represents one possible form of letter pattern employed in the practice of my invention;

Fig. 3 represents an alternative embodiment of my invention in a receiver;

Fig. 4 shows one possible arrangement of a transmitter for practicing my invention; and

Fig. 5 shows a detailoi one form of keyboard which may be used at 'a transmitter according to my invention.

in Fig. 1 the reference numeral, i, denotes a cathode ray tube havingthe customary fluorescent screen 2. The end of the tube is covered by a mask 3. A light spot produced on'the screen 2 by an electron beam originating at the electron gun is projected through the mask 3, and through a suitable optical system 5, upon a proection screen 5. Assuming that a predetermined pattern is impressed on the mask 3, e. g. by having certain portions thereof cut away, a repllca of this pattern will appear upon the pro- Jection screen 6. A person viewing the effect of signals in any other cathode ray tube which is not equipped with a similar mask, will obtain only a meaningless sequence of signals.

A simple pattern is illustratively shown in Fig. 2,

\ of the alphabet appear in irregular sequence and each letter is repeated several times at the same or diiierent places. The luminous spot will pick out in sequence first one and then another letter of the alphabet and thus convey the information desired.

In the arrangement shown in Fig. 3, the pattern is directly impressed upon a projection screen 6'. The different elements of the pattern are illuminated by projecting thereon through an optical system 5' light spots produced by the beam originating from the cathode ray tube 1.

ment of as much as 40 lines, the entire alphabet in the receiver can be repeated at least 30 times 1 in the pattern used, with retention of sufiicient clarity. Additionally, the electron beam within the receiving tube may be moved along a straight-line or over a simple geometrical path, by applying the incoming low frequency signals to thecustomary deflecting plates or coils which control such beam movement.

One possible arrangement suitable for transmitting such signals is shown in Fig. 5. A keyboard !!0, like that oi a typewriter, has keys such as the one shown at H, as representing the letter A, which keys will each, when depressed, cause respective voltage drops Ex and Ey across two resistors i5 and I6 (Fig. 5 which are arranged so as to be respectively of values of resistance proportional to the distance of the key from the edge of the keyboard I 0. The two voltages 50 derived can be used eitherto modulate two separate carrier waves, or can be used to modulate the same carrier wave. The signals so. transmitted can be separated in any con-.

venient manner, as well known in the art.

Alternatively, a camera tube 19, may be used in the tra'nsmitte;- and then the intelligence can be transmitted by illuminating a predetermined point of the pattern whenever a key is actuated.

As shown in Fig. 4, when a key N, like the one traverse aperture M and will be recorded at a corresponding point of the scanning field of camera tube l9, having passed through a suitable optical system, 20, before reaching camera tube it.

What is claimed is:

1. Secrecy communication system including mean for transmitting electrical impulses corre sponding to a predetermined position ofthe spot termined pattern of characters and means for optically superposing said code screen upon the screen of said cathode ray tube, whereby said predetermined position of said spot relative to said code screen corresponds to a given character upon said code screen, each sp t position being discrete and unconnected with any other spot position.

2. System according to claim 1, in which said code screen is of the cut-out type and is placed directly over the outer surface of said cathode ray tube screen.

3. System according to claim 1, in which said code screen is formed of material capable of transmitting light inat least a translucent manner, has said pattern of characters impressed thereupon in Opaque form and is placed directly over the outer surface of said cathode ray tube screen, whereby said spot illuminates and renders visible a predetermined character. I

4. System according to claim 1 in which said means for transmitting electrical impulses include a keyboard having a plurality of contactmaking keys thereupon, two resistors connected to each key, means to produce voltage drops across said resistors when said key is depressed, whereby the values of said respective voltage drops can be used to determine the locus of a point on a surface, and whereby said resistors function similarly to a set of coordinates and determine the two dimensional position of said spot at the cathode ray tube, each key being connected to resistor of a value difierent from any other resistors in the same row of keys.

5. System according to claim 1, in which said code screen is physically discrete and separated from said tube screen, and also including an optical projection system, whereby said spot i optically projected upon said code screen at a predetermined point thereof.

6. System according to claim 1, in which said means for transmitting electrical impulses include a substantially-rectangular keyboard having a plurality of contact-making keys thereupon,

two'resistors, extending vertically and horizontally from each key and having electrical values respectively equal to the abscissa and ordinate of the key to which they both are connected, and means for deriving from said two resistors electrical impulses determining at the cathode ray tube the two-dimensional position of said spot.

'7. Secrecy communication system including means for transmitting. electrical impulses corresponding to .a predetermined position of the spot of a cathode ray tube, said means including a camera tube and means for causing a luminous spot to appear sequentially in a plurality of predetermined discrete positions upon the creen of said tube, each position corresponding to a given character to be transmitted, and means for receiving said transmitted impulses.

8. System according to claim 1, wherein said pattern of characters covers substantially the entire surface of said code entiresurface is utilized for communication.

9. System according to claim 1, in which said code screen is formed of material capable of transmitting light in at least a translucent manner, has said pattern of characters impressed thereupon in opaque form and is placed directly over the outer surface of said cathode ray tube screen, and also including an optical projection system, whereby said spot is optically projectedupon said code screen at a predetermined point thereof, and whereby said pattern of characters is projected on said code screen, simultaneously with said spot.

CONSTAN'I'IN S. SZEGHO.

screen, so that said 

